The Democratic Party will gain a House majority in the midterms, but it will only be by a fraction, longtime Republican supporter and Home Depot co-founder Ken Langone predicted Thursday.

"I believe we may lose the House by a few seats," said Langone, a billionaire businessman and philanthropist, in a "Squawk Box" interview. "I think we'll keep the Senate."

But Langone also expects that Americans' perception of the Republican Party will be more favorable by 2020. That's because he expects President Donald Trump will settle the U.S. trade disputes with China and key trading partners by then.

Trump is attacking what he sees as unfair trade on a number of fronts, including tariffs on steel and aluminum imports. The president's moves have been met with retaliatory measures from the European Union, Canada, Mexico and China.

The vast majority of lawmakers and strategists from both major parties believe Democrats will at least pick up a chunk of Republican House seats in November or take a majority in the chamber.

Langone has previously warned Republicans that they could lose their majorities in the House and the Senate if lawmakers fail to seize on Trump-created opportunities. "We own the next 25 years as a nation [if we act]," he said in March 2017.

The U.S. economy has been booming under Trump. GDP is growing at a 3 percent-plus rate and the unemployment rate is near a 50-year low.

But Trump's rhetoric may not help as the GOP tries to stop Democrats from flipping 23 GOP-held seats and taking a House majority.

In CNBC's interview Thursday, Langone said Trump's economic agenda is fueling a resurgence in the economy that cannot be denied. "This economy is booming," he said. "I think he's made a lot of moves that are constructive to the economy."

When asked how Republicans could lose during the midterms with a roaring economy, Langone said, "You allow your opinion to infiltrate your position on things that are beneficial to your point of view."

"Give this president credit for something," he later said.

Before backing Trump in the 2016 presidential election, Langone first supported Chris Christie, who was governor of New Jersey at the time, and then Ohio Gov. John Kasich. Langone is also founder and CEO of investment bank Invemed Associates, which specalizes in health-care and high-technology companies.

— CNBC's Jacob Pramuk contributed to this report.

Watch: China is better off with a revised deal than no deal, says Ken Langone